Generate and compare checksum in OIC

Summary:

We have requirement to compare checksum value received from source application for input file with checksum value generated by OIC. We are using below function to generate checksum in OIC by passing file reference but it seems file reference gives different value each time. Is there any other way we should be following?

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

OIC Gen3

Code Snippet (add any code snippets that support your topic, if applicable):

function checksum_sha256(inputStr) {
  var sha256_result = oic.checksum.sha256(inputStr,"sha-256");
  return sha256_result;
}